Solenoid actuators are widely used in fuel injectors to move a control valve(s) to precisely control fluid connections within the fuel injector in order to control injection timing and injection quantities. As performance demands have crept upward, the industry has continued to seek new materials and assembly options to improve upon existing solenoid actuators. One strategy that has shown promise for improving performance includes utilizing soft powder metal in forming the stator core of the solenoid actuator. This material is known for exhibiting better magnetic permeability characteristics than ferromagnetic alloy counterparts. Unfortunately, the bonds between individual particles of powder in the stator core are weak, thus creating new potential problems with regard to erosion and fragmentation. This liberated powder material not only degrades the solenoid actuator performance, but can also lead to injector failure by particle debris inhibiting movement of various components and potentially blocking nozzle outlets of the fuel injector.
U.S. Patent publication 2009/0267008 teaches a solenoid actuator that uses a powder metal stator core that is partially plated with non-ferrous material to inhibit breakage and loss of powder particles during assembly and use. While the '008 patent publication teaches a strategy for protecting most of the powder metal stator core from fragmentation and loss of particles, the reference teaches an intentional exposure of the soft powder metal surface in the air gap region between the stator assembly and armature where fuel resides and swirls around with each actuation of the actuator, when in use. Thus, the '008 publication still teaches a structure with soft powder metal core directly in contact with moving fuel over the working life of the fuel injector, which may lead to erosion, degraded performance and potential failure by liberated powder particles lodging in critical locations within the fuel injector. Furthermore, while this reference teaches a strategy for protecting much of the soft powder metal stator core from breakage, it teaches the use of a non-ferromagnetic plating, which results in valuable space that could be used to carry magnetic flux instead being occupied by a protective plating that does not contribute to supporting the magnetic field.
The present disclosure is directed toward one or more of the problems set forth above.